OSPF questions

liven

Anyone know of a good online resource in regards to the 5 different network types ospf can support

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Netstudent

Check the cisco DOC cd. You can navigate from cisco.com or you can probably google "cisco, OSPF, network type, NBMA" and your first couple hits will probably be a cisco DOC. If you are studying for the CCNA, then the cisco DOCS are about as precise and specific as you can get for free.

liven

Cool thanks.

I also like the sites guys make (folks like you and me) were they put things in their own words.

Sometimes getting something phrased a little differently can make all the difference in the world.

Like the phrase:

please do not through sausage pizza away

For the OSI layers...

I know these little tricks don't exist for all the different topics. But still they are nice to have. Know what I mean?

Netstudent

Yes I know...it's always helpful to get multiple perspectives on complicated subjects. All you can do is browse around. Good luck.

hectorjhrdz

try this

http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080094e9e.shtml

Paul Boz

It may help you to learn the seven LSA types used by OSPFv2 before you try to learn the area types. The area types are designed to bound certain LSA types so if you know what each LSA type is for you can generally know how the areas work.

For example, stub areas won't permit any type 5 or type 7 LSA's (which are OSPF External Route LSA's) because a stub area only has one exit - connected to the OSPF domain. Type 5 and Type 7 LSA's deal with telling the OSPF domain about how to get to routes outside of the OSPF domain. If you have routers in a stub area that means that they have no direct connections out of the network so they have to send all traffic through the backbone area (area O). If that's the case, there's no point in telling the routers in the stub area about the external routes (advertised by the type 5 and type 7 LSA's) so the stub routers just drop those LSA's.

Here's a great URL with explanations of the OSPF LSA types. There are even some handy links at the bottom of the article that you can check out for further reading.

http://www.cramsession.com/articles/files/making-sense-of-ospf-area-9152003-1522.asp

It may be a little beyond the requirements of the CCNA to learn about the inner-workings of OSPF but if you really want to understand the material that they're asking you to learn about you should definitely put the time into learning a little more

liven

Paul Boz wrote:

It may help you to learn the seven LSA types used by OSPFv2 before you try to learn the area types. The area types are designed to bound certain LSA types so if you know what each LSA type is for you can generally know how the areas work.

For example, stub areas won't permit any type 5 or type 7 LSA's (which are OSPF External Route LSA's) because a stub area only has one exit - connected to the OSPF domain. Type 5 and Type 7 LSA's deal with telling the OSPF domain about how to get to routes outside of the OSPF domain. If you have routers in a stub area that means that they have no direct connections out of the network so they have to send all traffic through the backbone area (area O). If that's the case, there's no point in telling the routers in the stub area about the external routes (advertised by the type 5 and type 7 LSA's) so the stub routers just drop those LSA's.

Here's a great URL with explanations of the OSPF LSA types. There are even some handy links at the bottom of the article that you can check out for further reading.

http://www.cramsession.com/articles/files/making-sense-of-ospf-area-9152003-1522.asp

It may be a little beyond the requirements of the CCNA to learn about the inner-workings of OSPF but if you really want to understand the material that they're asking you to learn about you should definitely put the time into learning a little more

wow thanks.

I hope this is a little beyond the CCNA, just a lot more data to memorize. But none the less a very good resource!